Method of establishing a connection, as well as an exchange and a service control point

ABSTRACT

The invention concerns a method of establishing a connection via a communications network to a called terminal (TE) which is geographically located in the area (AREA) of two or more local line networks (LNA to LNC), as well as an exchange and a service control point for carrying out this establishment of a connection. A calling terminal requests a connection to the called terminal (TE) by means of a call request (CALL(N)) which is provided with a called number (N) assigned to the called terminal (TE). To establish the connection, that of the two or more local line networks (LNA to LNC) via which the called terminal (TE) can be reached, is determined by means of a learning procedure using the called number (N).

BACKGROUND OF THE INVENTION

[0001] 1. Technical Field

[0002] The invention concerns a method of establishing a connection viaa communications network to a called terminal which is geographicallylocated in the area of two or more local line networks, as well as anexchange for a communications network and a service control point forconnection to one or to several exchanges of a communications network.

[0003] 2. Discussion of Related Art

[0004] Presently the usual methods of establishing a connection willroute a call request to the subscriber station by means of a call numberof the called subscriber which is entered therein. In this case the callnumber provides the path through the communications network and isevaluated step by step along the path through the communicationsnetwork, i.e. it first addresses for example the local exchange area,then the subscriber's exchange, and then the station of the calledsubscriber within the numbering range of the subscriber's exchange.

[0005] However all of these methods of establishing a connection fail ifthe local line networks of different network operators share the callingrange in a subscriber line area but the requirement for call numberportability still remains. In this case call number portability meansthat a subscriber is able to change local line network operators withinhis subscriber line area and can take his call number with him to thenew network operator. The result is that there is no longer a fixedassociation between the local line network and the call number of acalled subscriber, which can be identified with the call number.

[0006] The invention now starts with a method of establishing aconnection in a deregulated network environment, as proposed in thereport “High level service description for number portability” of the“Public Network Operators-Interest Group”, Jun. 29, 1994 as a possiblesolution for achieving call number portability in the United Kingdom(UK).

[0007] Call number portability is achieved by translating the callnumber by means of call forwarding or by means of an IN service(IN=Intelligent Network). If a subscriber changes from one networkoperator to a second network operator within a local exchange area andwishes to take his call number with him, call forwarding is installed asa service in the local line network of the first network operator. Ifthis service identifies a call request with this call number, the callrequest is rerouted to the local line network of the second networkoperator. This rerouting takes place by entering a new call number intothe call request instead of the original call number, which addressesthe subscriber as a subscriber of the local line network of the secondnetwork operator.

[0008] In this case the relocated call number and the local line networkto which a call request with this call number is to be routed, must beentered into a data base by the network operator. The call forwardingservice is controlled by the data from this data base.

[0009] A disadvantage of this solution is that this data base whichassists the forwarding service must be continuously updated by thenetwork operator. If the data base updating is delayed, the concernedsubscriber can no longer be reached.

[0010] Further drawbacks result when the portability of call numbers isdemanded to a greater extent and therefore a large number of forwardingservices are provided by a communications network. All of theseforwarding services must then be synchronized by a master data base.This causes a large expense.

SUMMARY OF INVENTION

[0011] The task of the invention is to present an alternative method ofestablishing a connection in a communications network, to a terminalthat is located in the area of two or more local line networks.

[0012] According to a first aspect of the invention, a method ofestablishing a connection through a communications network to a calledterminal located in the geographical area of two or more local linenetworks, wherein a calling terminal requests a connection to the calledterminal by means of a call request which is provided with a callednumber assigned to the called terminal, and wherein that of the two ormore local line networks via which the called terminal can be reached isdetermined for the establishment of the connection, characterized inthat the local line network via which the called terminal can be reachedis determined by means of a learning procedure using the called number.

[0013] According to a second aspect of the invention, an exchange for acommunications network with a routing guidance device for controllingthe establishment of a connection via the communications network to thecalled terminal, wherein the routing guidance device is provided withreception means for receiving a call request with a called numberassigned to the called terminal, and with control means that aredesigned so that if the called terminal is assigned to a subscriber linearea, and its call number area is shared by two or more local linenetworks, that of the two or more local line networks via which thecalled terminal can be reached is determined for the establishment ofthe connection, characterized in that the control means are designed sothat the local line network via which the called terminal can be reachedis determined by means of a learning procedure using the called number.

[0014] According to a third aspect of the invention, a service controlpoint for connection to one or to several exchanges of a communicationsnetwork, with a receiving unit for receiving a call request, with acalled number assigned to a called terminal, and with control means thatare designed so that if the called terminal is assigned to a subscriberline area, and its calling range is shared by two or more local linenetworks of different network operators, they determine that of the twoor more local line networks via which the called terminal can bereached, characterized in that the control means are designed so thatthe local line network via which the called terminal can be reached isdetermined by means of a learning procedure using the called number.

[0015] The basic idea of the invention is that when a connection isestablished, the destination local line network is no longer determinedon the basis of the numbering plan of the called terminal's call number,but by a learning procedure using the called terminal's call number. Inthat case the number of the called terminal is generally a very logicaddress which is addressed by a terminal or by a subscriber assigned tothis terminal.

[0016] Thus the assignment of the call number of a terminal to a localline network no longer needs to be entered into a data base by thenetwork operator. Nor is any explicit updating of said data baserequired any longer. Rather the method of establishing a connectionprovides that the local line network which is assigned to a call numberis learned in accordance with the learning procedure.

[0017] Further advantages of the invention result when a communicationsnetwork provides a number of forwarding services. In that case theprovision of a central master data base is no longer required. Theservices learn in a rather decentralized manner the assignment of localline networks to the incoming call numbers they receive. Based on thisdecentralized learning procedure, the expense of providing a centralmaster data base and the expense of the communication for synchronizingthe distributed data bases via the master data base are absent.

[0018] Since a central component is omitted, namely the master database, the invention has increased fail-safety.

[0019] A failure of the central master data base would affect the entirecommunications network, while the failure of a learning-capable nodeonly affects one partial network in a large number of partial networks.

[0020] However it is also possible to support the learning procedurewith a master data base when using the method of establishing aconnection according to the invention. This leads to an acceleration ofthe learning procedure.

[0021] Another advantage is that the method of the invention toestablish a connection can be directly integrated into the routingguidance of exchanges and thus the cost of introducing this method ofestablishing a connection is low.

BRIEF DESCRIPTION OF THE DRAWING

[0022] The invention is explained in the following by means of twoconfiguration example with the help of the attached drawings, wherein:

[0023]FIG. 1 is a section of a block diagram of a communicationsnetwork.

[0024]FIG. 2 is a block diagram of an exchange according to theinvention for a first configuration example.

[0025]FIG. 3 is a block diagram of an exchange and a service controlpoint according to the invention for a second configuration example.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0026] The first configuration example explains the method of theinvention to establish a connection in a communications network with oneor with several exchanges according to the invention.

[0027]FIG. 1 illustrates a section of a communications network withthree trunk networks TN1 to TN3, and three local line networks LNA toLNC. The local line networks LNA to LNC connect the terminals of asubscriber line area AREA. Of these connected terminals only terminalTE, which is connected to the local line network LNC, is shown as anexample. Of the exchanges of the trunk networks TN1 to TN3 and the localline networks LNA to LNC, four exchanges TEX or LEXA to LEXC are shownas an example.

[0028] The trunk networks TN1 to TN3 represent conventional trunknetworks which are used to provide telephone communication betweenexchanges. The trunk networks TN1 to TN3 are respectively connected tothe local line networks LNA to LNC of the subscriber line area AREA, sothat a connection can be established between the local line networks ofdifferent subscriber line areas via each trunk network TN1 to TN3.

[0029] It is also possible for the local line networks LNA to LNC to beonly connected to one trunk network and in this way there is nopossibility of dialing a trunk and therefore a trunk network operator.

[0030] The local line networks LNA to LNC are conventional line networksfor connecting telephone terminals and private branch exchanges.Possible telephone terminals in that case are telephones and faxmachines, but also modems and interface cards for connecting dataprocessing installations. They can be analog as well as ISDN (IntegratedServices Digital Network) terminals. The terminal TE is such a terminal.

[0031] The local line networks LNA to LNC are made up of one or ofseveral subscriber exchanges. Of these subscriber exchanges either theexchange LEXA, LEXB or LEXC is shown. All the terminals of subscribersassigned to one of the local line networks LNA to LNC are connected viasubscriber lines to such a subscriber exchange of the respective localline network. Larger local line networks may also contain transitexchanges because of the increased traffic load. Transverse linesinterconnect the exchanges of a local line network and one or severaltransit exchanges of the trunk networks TN1 to TN3.

[0032] It is also possible to interconnect exchanges of the local linenetworks LNA to LNC by means of transverse lines.

[0033] It is also possible that the local line networks LNA to LNC areradio networks, for example according to the GSM (Global System forMobile Communications) standard, or according to the DECT (DigitalEnhanced Cordless Telephone) standard. Such radio interfaces can also bepart of one or several exchanges in one of the local line networks LNAto LNC, i.e. only some of the subscribers of this local line network areconnected to one or to several radio networks.

[0034] The local line networks LNA to LNC are assigned to differentnetwork operators. Since they cover the same subscriber line area AREA,for example the same local network area, the local line networks LNA toLNC share the numbering range of the subscriber line area AREA. Thelocal line networks LNA to LNC are therefore available in parallel toeach other to the subscribers who reside in the same geographical areaunder the same local network identity. In this way the subscribers canchoose to which local line network LNA to LNC their terminal isconnected and by means of this selection determine the local linenetwork operator and thereby the conditions that apply to the subscriberline.

[0035] The following describes the layout of a connection from a callingterminal of the communications network to the terminal TE via the trunknetwork TN1.

[0036] The calling terminal sends a call request with a call number N,which identifies the called terminal TE, to the subscriber exchange towhich is connected.

[0037] It is also possible that the call number N is a logical networkaddress or an address that identifies the called subscriber.

[0038] The subscriber exchange routes the call request as a signallingmessage CALL(N) via the no. 7 signalling system to the trunk networkTN1. The trunk network TN1 then routes the signalling message CALL(N) tothe exchange TEX representing the transit exchange, whereby the localline networks LNA to LNC are connected to the trunk network.

[0039] The routing of the signalling message CALL(N) from exchange toexchange and finally to the exchange TEX is controlled by the routingguidance functions of these exchanges. These routing guidance functionssuccessively evaluate the call number N from exchange to exchange. Thusfor example the subscriber exchange determines from the first digits ofthe dialed number that the signalling message CALL(N) should be routedto the pertinent transit exchange of the trunk network TN1; this transitexchange then determines from the next digit or digits of the callnumber to which other exchanges of the trunk network the signallingmessage CALL(N) should be routed, and so forth.

[0040] The exchange TEX decides about the further routing of thesignalling message CALL(N) in a different way. The exchange to which thesignalling message CALL(N) is routed is determined on the basis of alearning procedure. This learning procedure comprises the followingsteps:

[0041] The exchange TEX checks successively which of the local linenetworks LNA to LNC of the call number N has a terminal assigned to it.To that end it sends a signalling message REQ(N) with the call number N,or the part of the call number N which corresponds to the numberingrange of the subscriber line area AREA, one at a time respectively to anexchange of the local line networks LNA to LNC, for example first to theexchange LEXA, secondly to the exchange LEXB and thirdly to the exchangeLEXC.

[0042] It is also possible to send the signalling message REQ(N) inparallel to these exchanges.

[0043] After it receives the signalling message REQ(N), the respectiveexchange LEXA, LEXB or LEXC checks in each case whether or not asubscriber line with the call number N is present in the local linenetwork LNA, LNB or LNC, and then sends a return message containing thisinformation back to the exchange TEX. By evaluating these receivedreturn messages, the learning procedure obtains the information to whichof the local line networks LNA to LNC of the subscriber line area AREAit must route the signalling message CALL(N), i.e. via which of thelocal line networks LNA to LNC the connection to the terminal TE shouldbe established.

[0044] The signalling message REQ(N) is the call request to establish aconnection in accordance with the no. 7 signalling system. This has theadvantage that the call request no longer needs to be additionally sentto this exchange. It is however possible for this message to be one thatis specified for this function proper, which is also transmitted via theno. 7 signalling system.

[0045] The signalling message REQ(N) is processed in the local linenetworks LNA to LNC as follows:

[0046] For example if the exchange LEXA is the only exchange of thelocal line network LNA, all the subscriber lines of this network areconnected thereto and its routing guidance contains a list definingwhich call number is assigned to what exchange. To check, it searchesthis list and recognizes if the part of the call number N thatcorresponds to the numbering range of the subscriber line area AREA isnot listed as a call number in the list. In that case it sends a returnmessage UNEQ to the exchange TEX. The return message UNEQ is sent to theexchange TEX as the no. 7 message via the no. 7 signalling system inthis case.

[0047] For example if the exchange LEXB is one of several exchanges inthe local line network LNA, the exchange LEXB, like the exchange LEXA,checks whether a subscriber line with the call number N is availabletherein. If this is not the case, it routes the call request CALL(N) tothis or to one of the other exchanges in the local line network LNB.This other exchange then performs an analog check.

[0048] The selection of the exchange to which the exchange LEXB routesthe call request can be made on the basis of a numbering plan. In thatcase the selection is made based on an assignment of a predeterminedfrontal sequence of digits in the call number N as the sequence ofdigits which identifies a predetermined exchange in the local linenetwork LNB.

[0049] A second possibility is that the exchange LEXB has a listdefining which of the call numbers in the local line network LNB isassigned to which one of the subscriber lines in the local line networkLNB. In that case it is also possible for the check to be performed bythe exchange LEXB alone by evaluating this list.

[0050] A third possibility is that the exchange LEXB performs a learningprocedure that is analogous to that carried out by the exchange TEX, andby means of this learning procedure prepares a list that defines whichcall number is assigned to which one of the exchanges in the local linenetwork LEXB.

[0051] It is also possible for each or several of the exchanges in thelocal line network LNB to have a connection to the exchange TEX. In thatcase the exchange TEX would successively send the call request REQ(N) tothese exchanges. Upon receiving this request, the individual exchangeswould perform a check that is analogous to the check performed by theexchanges LNA or LNB.

[0052] The terminal TE is also not connected via the local line networkLNB, and thus a return message UNEQ is also sent to the exchange TEX bythe exchange LEXB.

[0053] The exchange LEXC knows that a terminal with the call number N isconnected to it, namely the terminal TE. This way after receiving thesignalling message REQ(N) it sends a return message SUC to the exchangeTEX. In this case the return message SUC is sent as the no. 7 messagevia the no. 7 signalling system.

[0054] Sending back the return message SUC could also be omitted. Thelack of a return message, which is diagnosed for example after a timerhas run out, can be used as the sign that the called terminal isconnected through the local line network LNC.

[0055] By sending a return message SUC, the exchange LEXC routes a callto the terminal TE. If the subscriber lifts the receiver of terminal TE,the exchange LEXC causes a connection to be established backwardsbetween the terminal TE and the calling terminal in accordance with thepath laid by the call request CALL(N) through the communications networkfrom the calling to the called terminal.

[0056] It is also possible for a user information channel to be switchedone by one through the communications network parallel to routing thecall request CALL(N) further through the communications network, i.e.the connection is made in parallel and in accordance with the callrequest CALL(N).

[0057] During the establishment of the connection it is also possiblefor other or further exchanges of the communications network todetermine the exchange to which they are routing a call request inaccordance with the method performed by the exchange TEX. All of theseexchanges face the problem that the call request is addressed to aterminal in the subscriber line area AREA and that they must determinevia which one of the local line networks LNA to LNC a connection to thisterminal should be established. Such exchanges could for example beexchanges of the local line networks LNA to LNC, which are connected viaa transverse line to one or to several exchanges of one or several ofthe other local line networks LNA to LNC, and thus participate in theestablishment of a connection between the terminals that are connectedto different local line networks LNA to LNC.

[0058] The detailed performance of the learning procedure during theestablishment of the connection will now be explained by means of FIG.2. FIG. 2 illustrates the exchange TEX with two attachment units PH, aswitching network SW and a controller RC which is responsible for therouting guidance.

[0059] The attachment units PH provide functions that enable thesubscriber line connection of terminals and particularly the connectionof transverse line bundles to other exchanges. For example the exchangesLEXA to LEXC are connected through the attachment units PH to theexchange TEX by means of transverse line bundles.

[0060] The attachment units PH and the controller RC exchange data viathe switching network SW. The controller RC controls the switchingnetwork SW. It contains a communications unit KOM and two control unitsRF and CONTR1.

[0061] The communications unit KOM contains the necessary functionalhardware and software groups which are required to receive and sendsignalling messages via the switching network SW. These functionalgroups in particular enable the reception of the call request CALL(N)and the return messages SUC and UNEQ, and sending the signalling messageREQ(N).

[0062] The control units CONTR1 and RF comprise control programs whichrun on the data processing platform of the exchange TEX. In this casethe control unit RF is responsible for controlling the learningprocedure, and the control unit CONTR1 is responsible for the remainingpart of controlling the establishment of a connection via the exchangeTEX.

[0063] If the control unit CONTR1 receives a call request, for examplethe call request CALL(N), it determines from the call number containedin the call request whether the request is addressed to a terminal ofthe subscriber line area AREA, and therefore the local line network viawhich this terminal can be reached must be determined. If this is thecase, a message is sent to the control unit RF which then determinesthis local line network and causes the establishment of the furtherconnection through this local line network via the control unit CONTR1.

[0064] The control unit RF contains a control logic CONTR2 and a database DB.

[0065] The control logic CONTR2 controls sending the signalling messagesREQ(N) in accordance with the method described by FIG. 1. If the controllogic CONTR2 receives a positive return message SUC, it stops thefurther sending of signalling messages REQ(N) to exchanges of the stillremaining local line networks. In this case the sequence whereby thesignalling messages REQ(N) are sent to the exchanges of the local linenetworks can be randomly selected, or it can be specified for all callrequests.

[0066] It is advantageous to determine these sequences by statisticallyevaluating the attempts to establish a connection to terminals of thesubscriber line area. For example a signalling message REQ(N) is firstsent to an exchange of the local line network via which most of theconnections are established, etc. The sequence can be adaptively fittedto the subscriber response by continuously and statistically evaluatingthe attempts to establish a connection to the terminals of thesubscriber line area.

[0067] It is also possible for the signalling message REQ(N) to be sentto the local line network via which most of the connections areestablished and, if this attempt is not successful, the signallingmessage REQ(N) is then sent in parallel to all the remaining local linenetworks.

[0068] Data concerning the assignment of call numbers to local linenetworks of the subscriber line area AREA are stored in the data baseDB. While the connection is being established, if the learning proceduredetermines by means of the above described method the particular localline network via which a terminal with a predetermined call number isconnected, this call number and this local line network are stored as anassignment in the data base DB. When the learning procedure is beingperformed, the data base DB is first searched to determine whether italready stores an assignment of a local line network to the call numbercontained in the call request. If this is the case, the assignment isused to establish the connection. If this assignment is no longercorrect, for example because a subscriber has changed his local linenetwork operator, this is determined upon reception of the returnmessage UNEQ. In that case the learning procedure is performed asdescribed earlier, i.e. successive signalling messages REQ(N) are sentout.

[0069] It is also possible to omit the data base DB and to perform thelearning procedure solely by sending out the signalling messages REQ(N)and by receiving the return messages SUC and UNEQ. But using the database DB has the advantage of lessening the signal load on thecommunications network.

[0070] It is furthermore possible to provide the assignments with a timestamp and to delete an assignment from the data base DB after it has notbeen requested for a long period of time, or it has been stored in thedata base DB for a long period of time. The deletion or the input of anassignment in the data base DB could also be a function of the frequencyof the assignment requests. When such deleting strategies are used, therequired storage space of the data base DB can be considerably reducedwithout significantly increasing the signal load on the communicationsnetwork.

[0071] A further possibility is for the control logic CONTR2 to alsohave access to a master data base while the learning procedure is beingperformed. Network-wide there could be one or even several of suchmaster data bases. In that case it is an advantage to provide a masterdata base for locally adjacent exchanges TEX.

[0072] An access to this master data base takes place for example if noinput or no valid input of a call number can be found in the data baseDB, and the local line network cannot be found after one or severalsignalling messages REQ(N) have been sent out. If no assignment or novalid assignment is stored in the master data base either, sending theremaining signalling messages continues. If an assignment issubsequently determined, it is entered into the data base DB and intothe master data base.

[0073] The second configuration example explains the performance of themethod of the invention to establish a connection in a communicationsnetwork with one or several service control points of the invention.

[0074] In the second configuration example the establishment of aconnection is performed as in FIG. 1, with the difference that theexchange TEX is replaced by a service switching point SSP and a servicecontrol point SCP.

[0075]FIG. 3 illustrates the service switching point SSP and the servicecontrol point SCP which communicate with each other, for example inaccordance with the IN architecture (IN=Intelligent Network).

[0076] It is also possible for two or more service switching points SSPto have access to the service control point SCP and in this way tocentrally control the method of the invention to establish a connectionin several exchanges by means of the service control point SCP.

[0077] The service control point comprises the attachment units PH, theswitching network SW and a controller RC′ which comprises the controlunit CONTR1, the communications unit KOM and a control unit SSF.

[0078] The attachment units PH, the switching network SW, the controlunit CONTR1 and the communications unit KOM are designed in accordancewith FIG. 2.

[0079] The control unit SSF is used to link the service control pointSCP with the controller RC′. It contains a control logic CONTR3 and acommunications unit KOM′.

[0080] The communications unit KOM′ provides the necessary communicationservices for communication with the service control point SCP via theno. 7 signalling network or via any other data network, for example aX.25 packet network.

[0081] The control logic CONTR3 works together with the control unitCONTR1 and with the communications unit KOM like the control logicCONTR2 in FIG. 2, with the difference that the actual control functionsare provided by the service control point SCP.

[0082] The service control point SCP also contains the communicationsunit KOM′, the control logic CONTR2 and the data base DB. Beyond that italso contains functional groups that work together with the controllogic CONTR3 and CONTR2, and enable control by means of the controllogic CONTR2 of a method of establishing a connection which is carriedout via the controller RC′. These functional groups, the control logicCONTR3 and the communications unit KOM′ can work together in accordancewith the IN architecture for example.

[0083] The control logic CONTR2 and the data base DB are configured asshown in FIG. 2. Thus the establishment of a connection is made inaccordance with FIG. 1 and FIG. 2, with the difference that the learningprocedure is performed by functional groups of the service control pointSCP.

1. A method of establishing a connection through a communicationsnetwork to a called terminal (TE) located in the geographical area(AREA) of two or more local line networks (LNA to LNC), wherein acalling terminal requests a connection to the called terminal (TE) bymeans of a call request (CALL(N)) which is provided with a called number(N) assigned to the called terminal (TE), and wherein that of the two ormore local line networks (LNA to LNC) via which the called terminal (TE)can be reached is determined for the establishment of the connection,characterized in that the local line network (LNC) via which the calledterminal (TE) can be reached is determined by means of a learningprocedure using the called number (N).
 2. A method as claimed in claim1, characterized in that the two or more local line networks (LNA toLNC) form a subscriber line area (AREA) having a common number range,with the two or more local line networks (LNA to LNC) sharing saidcommon number range.
 3. A method as claimed in claim 1, characterized inthat the two or more local line networks (LNA to LNC) are operated bydifferent network operators.
 4. A method as claimed in claim 1,characterized in that the learning procedure involves checkingsuccessively whether in the local line networks (LNA to LNC) a terminalis assigned to the called number (N).
 5. A method as claimed in claim 4,characterized in that the check is made by sending to the respectivelocal line network (LNA to LNC) a call request (REQ(N)) for theestablishment of a connection to a terminal with the called number (N).6. A method as claimed in claim 5, characterized in that in response tothe call request (REQ(N)), the respective local line network (LNA, LNB)provides a return message (UNEQ) if no terminal is assigned to thecalled number (N) in the respective local line network (LNA, LNB).
 7. Amethod as claimed in claim 4, characterized in that if the check ispositive, the checked local line network (LNC) is determined as thelocal line network in which a terminal is assigned to the called number.8. A method as claimed in claim 4, characterized in that if the check ispositive, the called number (N) and, in association therewith, thechecked local line network (LNC) are stored in a database (DB).
 9. Amethod as claimed in claim 4, characterized in that in the learningprocedure, the database (DB) is first searched to determine whether thecalled number (N) is stored therein together with an associatedsubscriber line network.
 10. A method as claimed in claim 4,characterized in that for the check, messages (REQ(N), UNEQ, SUC) areexchanged with one or more of the local line networks (LNA to LNC) viathe no. 7 signaling system.
 11. A method as claimed in claim 1,characterized in that the learning procedure is controlled by an INservice.
 12. A method as claimed in claim 1, characterized in that thelearning procedure is controlled by the routing guidance (RC) of anexchange (TEX).
 13. An exchange (TEX) for a communications network witha routing guidance device (RC) for controlling the establishment of aconnection via the communications network to the called terminal (TE),wherein the routing guidance device (RC) is provided with receptionmeans (KOM) for receiving a call request (CALL(N)) with a called number(N) assigned to the called terminal (TE), and with control means (RF,CONTR1) that are designed so that if the called terminal (TE) isassigned to a subscriber line area (AREA), and its call number area isshared by two or more local line networks (LNA to LNC), that of the twoor more local line networks (LNC) via which the called terminal (TE) canbe reached is determined for the establishment of the connection,characterized in that the control means (RF, CONTR1) are designed sothat the local line network (LNC) via which the called terminal (TE) canbe reached is determined by means of a learning procedure using thecalled number (N).
 14. An exchange (TEX) as claimed in claim 13,characterized in that the exchange (TEX) is located in thecommunications network at the transition point between the remote andthe local network plane.
 15. A service control point (SCP) forconnection to one or to several exchanges (TEX) of a communicationsnetwork, with a receiving unit (KOM′) for receiving a call request(CALL(N)), with a called number (N) assigned to a called terminal (TE),and with control means (CONTR2, DB) that are designed so that if thecalled terminal (TE) is assigned to a subscriber line area (AREA), andits calling range is shared by two or more local line networks (LNA toLNC) of different network operators, they determine that of the two ormore local line networks (LNC) via which the called terminal (TE) can bereached, characterized in that the control means (CONTR2, DB) aredesigned so that the local line network (LNC) via which the calledterminal (TE) can be reached is determined by means of a learningprocedure using the called number (N).